Yes there other reasons. Like, I have had customers requesting 30+ megapixels files in their RFPs. They don't know, somebody told them about the D800 and the 36 megapixels. A 36 megapixels photos must be twice better than an 18 megapixels photo, so they request it.

BTW, notice that although the 36 megapixels is "twice better" than the 18mpx, they do not want to pay twice more for a "twice better" photo.